For some years, different types of radio networks for wireless communication have been developed to provide radio access for various wireless terminals and devices in different areas. The radio networks are constantly improved to provide better coverage and capacity, to meet demands of increasingly advanced services and devices, e.g. smartphones and tablets, which may require considerable amounts of bandwidth and resources for data transport and control signaling in the networks. A limiting factor for capacity of a radio network, or for radio communication in general, is the amount of available radio resources, e.g. in terms of time, frequency bandwidth and transmit power, and the capacity of a radio network can be improved by more efficient usage of such radio resources.
In this disclosure, the term “User Equipment, UE” will be used to denote any wireless device capable of communicating radio signals with a radio network. For example, a UE in this context may be a mobile phone handled by a human or a Machine-to-Machine, M2M, type of device operating automatically such as a sensor, counter or measuring entity. Further, the term “network node” will be used to denote any node of a radio network capable of communicating radio signals with a UE. For example, a network node in this context may be a base station, an eNodeB, an access point, a relay, etc., depending on the terminology and type of network used. However, the UEs and network nodes described herein are not limited to the above examples.
As mentioned above, it is of interest for network operators to improve capacity in their networks by utilizing the available radio resources as efficiently as possible. Another area of interest is to ensure correct and reliable reception when data is transmitted from a data sending node to a data receiving node, if this is deemed important. The amount of errors in the data communication can be reduced by adding extra control bits to the data which can be used for error correction and/or for checking that the received data has been received correctly. A common method for error detection is the well-known Cyclic Redundancy Check, CRC, where the data sending node attaches CRC bits, also referred to as parity check bits, to the data indicating basically a checksum of the transmitted data which can be checked by the data receiving node to verify correct reception of the data. This procedure is commonly referred to as CRC attachment.
For control messages, such as assignments of radio resources to UEs transmitted on a control channel, CRC attachment can also be utilized by a network node to address a message to a particular UE, by embedding an identity associated with the UE in the CRC bits of the CRC attachment. An identity called Radio Network Temporary Identity, RNTI, is commonly used as UE identity in the CRC attachment of control messages. Thereby, only the addressed UE will verify the message based on its identity, e.g. its RNTI, and a CRC check made by other UEs using other identities, e.g. RNTIs, will not verify the message since their identities do not match the CRC attachment of the message. It is also possible for more than one UE to use the same UE identity, e.g. RNTI, thus enabling the network node to address a group of UEs in the same message.
FIG. 1 illustrates an example of how the above-described CRC attachment may be created by a network node in a conventional manner, for addressing a message 100 with payload bits to a certain UE. The number of payload bits in the message 100 is denoted A. The network node creates a set of parity bits 102 based on the payload in the message 100, typically a checksum of the payload bits. The network node also obtains a set of RNTI bits 104 from the RNTI of the UE, and merges the parity bits 102 and the RNTI bits 104 by means of an operation called “bit-wise modulo 2 ”, which generates a set of CRC bits 106 in which the parity bits 102 and the RNTI bits 104 are thus embedded. The number of CRC bits 106 is denoted L. The network node then transmits the message 100 with the CRC bits 106 attached in a transmission 108. The total number of bits in transmission 108 is denoted B which is thus the sum of A and L, as indicated in the figure. The above-mentioned bit-wise modulo operation is well-known in the art and as an example the bit-wise modulo 2 of “001” and “101” equals “100”.
However, it is a problem that a large amount of control messages must be transmitted to instruct various UEs to operate according to the control messages, particularly when several different UEs need to be instructed in different ways, e.g. individually. The transmission of such control messages and other dedicated messages, which may be referred to as signaling overhead, naturally consumes precious radio resources which could otherwise be available for data transport, thereby limiting the maximum capacity of the radio network. Further, much interference may be generated in the network by the transmission of numerous control messages and other messages to different UEs.